Inhalable medicaments, such as, for example, those for the prophylactic or therapeutic treatment of asthma or bronchitis, are commonly administered to patients using a metered dose inhaler (MDI). An MDI generally comprises a container housing the medicament, an axially extending vent tube from an internal valve, and a hollow actuator unit that houses the container and feeds the medicament to the patient via its outlet portion. The medicament is commonly packed in the container with a suitable propellant, such as, for example, a substance capable of forming a liquid under pressure and entering the gas phase at low pressure.
In use, the patient brings the outlet of the actuator to his/her mouth, depresses the container relative to the actuator, thereby activating the internal valve to dispense a measured dose of medicament into the patient's mouth. In this arrangement, it is often necessary for the patient to coordinate his/her inhalation with the depression of the container to ensure that a sufficient dose of the medicament enters the patient's airway. The medicament will generally include a liquid/gas mixture of propellant, wherein small drops of medicament/propellant mixture enter the patient's airway with the medicament and rapidly projected particles of medicament/propellant mixture are deposited in the throat and mouth and are swallowed. Accordingly, the need to coordinate the dispensing of medicament with the patient's inhalation, and the dispensing of medicament/propellant mixture from the MDI, reduce the efficiency of treatment. Moreover, there is a need to allow the deceleration and dispersal of particles to minimize deposition in the throat and mouth.
To enhance the efficacy of treatment, a spacer is commonly attached to the outlet of the actuator. Alternatively, the actuator is removed and the spacer is attached directly to the container via the vent tube. A spacer is a simple expansion chamber conveniently in the form of a small cylinder, conical or pear-shaped, into which a medicament that is dispensed from an MDI can be held prior to inhalation by a patient.
In use, one end of a spacer is attached to the outlet of the MDI, and the other end of the spacer is received into the patient's mouth. A sealing engagement between the spacer and the MDI is required to minimize drug/medicament leakage, thereby ensuring that an adequate dose of medicament is received by the spacer unit. The patient depresses the container of the MDI relative to the actuator, thereby activating the internal valve to dispense a measured dose of medicament into the spacer. In a separate action to dispensing of the medicament from the MDI, the patient inhales air/medicament/propellant mixture from the spacer into his/her airway. Accordingly, the spacer provides an advantage in so far as there is no need for the patient to coordinate his/her inhalation with the depression of the container of the MDI. Additionally, the spacer facilitates the deceleration and dispersal of particles of the medicament into smaller particles, for efficient inhalation.
As will be known to those skilled in the art, a rigid material, such as, for example, polycarbonate, is preferred for construction of a spacer. This is because such a rigid material confers strength and durability on the device. Additionally, polycarbonate is heat-resistant, facilitating steam sterilization and washing of the device in a dishwasher.
Standard spacers are constructed with at least two separate pieces: (i) a hollow inlet member having an opening for attaching an MDI actuator to facilitate the flow of medicament from the MDI to the spacer unit, (ii) a hollow outlet member having an opening for attaching a mouthpiece or mask to facilitate delivery of the medicament to the patient, and often (iii) a separate barrel-shaped element between elements (i) and (ii). During assembly, the components are snap-locked; or screwed together in sealing engagement to form an interior space for holding the medicament during use, and two openings to facilitate the flow of a medicament through the assembled unit.
Spacer devices are described in detail by Nowacki et al. in U.S. Pat. No. 4,470,412; and by InfaMed Limited in international Application No. PCT/AU99/00290.
Notwithstanding the advantages of using a spacer, such devices do increase the costs associated with treatment relative to the cost of the MDI alone. Moreover, as drug companies generally provide their MDI with an actuator having an outlet of a particular shape, not all actuator outlets are capable of being in sealing engagement with all spacer units. Accordingly, it is highly desirable for a spacer unit to be universally adaptable to all MDI devices.
One solution to this problem is to provide an “adaptor” or “back piece” that attaches to the end of the spacer and is capable of attaching to a plurality of actuator outlets. For example, the adaptor described in U.S. Pat. No. 5,848,588 (Trudell Medical International) comprises resilient, flexible material such as a rubber or the like, wherein concentric cylinders cover and grip the end of a cylindrical spacer, and a transverse membrane extends inwardly therefrom and is provided with a central opening, and straight and inwardly-directed ribs for receiving and gripping the outlet of the MDI. Pairs of the ribs have cross bracing, to control stretching of the diaphragm so that it provides a proper seal with an inserted MDI, whilst the radial inner ends of the ribs provide support for the MDI.
Spacer devices that do not require a separate adaptor have been designed to fit most known MDI units, with varying success. Generally, the provision of a universally-adaptable spacer of rigid construction has been avoided because such a device would have been prone to breaking and/or cracking, during fitting to MDI outlets of different shapes.
Occasionally, rigid spacer devices have been designed with prong-shaped protrusions to maximize flexure of the spacer to accommodate an MDI actuator. These protrusions are inherently brittle when made of a rigid plastic and are adaptable to very few types of actuators.
Accordingly, known spacers that are usable with a plurality of MDI devices generally require prior removal of the MDI container from the manufacturer's actuator, and subsequent fitting of the container to the spacer unit. Poor sealing between the vent tube of the MDI and the spacer may result during such procedures.
Alternatively, it is known to fit the spacer with a flexible inlet to accommodate various shaped MDI actuators. In fact, most conventional spacers that fit a plurality of different MDI actuators provide a flexible adaptor end that stretches or is compressed relative to the actuator. However, such an arrangement cannot be easily produced as an integral unit, because the spacer is generally made from rigid material, such as, for example, polycarbonate. This is a considerable disadvantage in terms of production of the device, because of the additional costs associated with producing separate pieces. Additionally, by providing a spacer in multiple pieces, with an additional rubber-like adaptor end piece, assembly of the device is made more complex, and requires additional effort either by the production team or the end user.